JP6816361B2 - Fine charcoal-fired boiler equipment - Google Patents

Description

The present invention relates to, for example, a boiler facility for burning pulverized coal of coal, particularly a boiler facility for co-firing woody biomass and pulverized coal.

In a boiler facility that uses coal (pulverized coal) as fuel, it is desirable to supply the coal stored in the coal silo to the pulverized coal machine by a coal feeder in order to make the grain size suitable for burning the coal with a burner. Grind below grain size. The coal crushed by the pulverized coal machine is discharged from the pulverized coal machine along with the combustion air supplied to the pulverized coal machine by the primary ventilator. Then, this pulverized coal is supplied to the burner, supplied into the furnace of the boiler equipment, and burned.

By the way, in recent years, from the viewpoint of reducing global warming gas emissions, the development of technology to reduce fossil fuel consumption by burning so-called woody biomass such as wood pellets and wood chips obtained from thinned wood and waste wood in boiler equipment. Is underway.

When using this woody biomass as fuel for boiler equipment, it is most efficient to crush it with coal in a pulverized coal machine and burn it in the boiler equipment. In addition, since the installed capacity of the pulverized coal machine usually has a margin of about 10% to 20%, there is no particular problem in terms of the installed capacity even if woody biomass is additionally added to the pulverized coal machine.

However, unlike coal, woody biomass has compressibility and has a different specific gravity from coal, so that there is a problem that it is difficult for a pulverized coal machine for crushing coal to crush it to a desired particle size (particle size suitable for combustion). In such a case, the woody biomass that has not been pulverized to a desired particle size is not discharged from the pulverized coal machine by the combustion air from the primary ventilator, and remains in the pulverized coal machine. As a result, the operation of the pulverized coal machine cannot be continued, and it may be necessary to reduce the load on the boiler equipment.

Therefore, in Patent Document 1, in order to crush woody biomass to a particle size suitable for combustion and to burn it efficiently, a crushing means for crushing woody biomass and a burner for burning woody biomass are used separately from a pulverized coal machine for crushing coal. It is proposed to provide. Further, Patent Document 1 also proposes that woody biomass is heated and then crushed by a crushing means, and if the particle size after crushing does not satisfy the standard value, it is crushed again by the crushing means.

Further, Patent Document 2 also discloses a biomass co-firing boiler provided with a dedicated biomass-burning burner. Further, Patent Document 3 discloses a processing method for efficiently using woody biomass containing bamboo, and Patent Document 4 describes a pretreatment method for woody biomass using a white-rot fungus having lignin resolution. It is disclosed.

Japanese Unexamined Patent Publication No. 2014-37897 Japanese Unexamined Patent Publication No. 2013-133944 Japanese Unexamined Patent Publication No. 2012-219130 Japanese Unexamined Patent Publication No. 2008-6372

However, it costs a lot to provide a dedicated device for crushing and burning woody biomass as in each of the above patent documents. In addition, woody biomass has a much lower calorific value as fuel than coal, and is inferior in energy efficiency. Therefore, it cannot be said that operating a facility dedicated to woody biomass has a great advantage from the viewpoint of energy efficiency.

Therefore, the use of woody biomass as fuel in the current boiler equipment is such that even if it remains inside the pulverized coal machine, it does not hinder the continuation of operation of the pulverized coal machine, specifically, about 2 to 3 mass% of pulverized coal. It is only supplied to the machine and co-fired with pulverized coal in a burner. Therefore, there is a need to develop an efficient combustion method for woody biomass in boiler equipment.

The present invention has been made in view of this point, and an object of the present invention is to efficiently burn woody biomass in a pulverized coal-fired boiler facility.

The present invention for achieving the above object is a pulverized coal-fired boiler facility for burning pulverized coal of coal with a burner, the pulverized coal machine for crushing the coal to produce pulverized coal, and the pulverized coal. A coal supply device that supplies coal to the machine, a woody biomass supply device that supplies woody biomass having a particle size equal to or less than a specified value to the pulverized coal machine, pulverized coal produced by the pulverized coal machine, and the pulverized coal machine. It is characterized by having a fuel supply pipe for introducing the supplied woody biomass into the burner in a mixed state.

As a result of diligent studies by the present inventors, woody biomass is mainly composed of fibrous material called cellulose, which is one of the causes that makes it difficult to crush woody biomass in a pulverized coal machine for crushing coal. I got the finding that there is. Based on this finding, the present inventors diligently studied a method for efficiently crushing woody biomass with a pulverized coal machine for coal crushing, and set the particle size of the woody biomass supplied to the pulverized coal machine to a specified value or less. That is, the idea was that if the cellulose of the woody biomass was cut into pieces of a predetermined size or less, the woody biomass could be easily crushed in the pulverized coal mill and the woody biomass could be prevented from remaining. The present invention is based on this idea, and according to the present invention, since the pulverized coal machine has a woody biomass supply device having a grain size equal to or less than a specified value, the pulverized coal machine is provided with woody biomass. Even if it is supplied, it will not be difficult to continue the operation of the pulverized coal machine. Therefore, the amount of woody biomass supplied to the pulverized coal machine can be increased as compared with the conventional case. As a result, it is possible to efficiently burn woody biomass in a pulverized coal-fired boiler facility without providing a combustion facility or the like dedicated to woody biomass.

In the pulverized coal-fired boiler device, the woody biomass supply device may further have a drying function. Further, the specified value of the particle size of the woody biomass supplied to the pulverized coal machine may be 4 meshes or more in terms of the number of meshes of the sieve. The term "4 meshes" in terms of the number of meshes of the sieve means a particle size such that the mesh size of the sieve passes through the sieve having a mesh size of approximately 4.76 mm.

According to the present invention, woody biomass can be efficiently burned in a pulverized coal-fired boiler facility, and the co-firing rate can be increased.

It is a system diagram which shows the outline of the structure of the pulverized coal-fired boiler equipment which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is an explanatory diagram showing an outline of the configuration of the boiler equipment 1 according to the present embodiment. The boiler equipment 1 in the present embodiment is a pulverized coal-fired boiler that uses pulverized coal obtained by crushing coal as fuel.

The boiler equipment 1 includes a furnace 2 for burning coal, a fuel supply system 3 for supplying coal and woody biomass as fuel to the furnace 2, and combustion air for coal combustion to the furnace 2, and coal from the furnace 2. It has a ventilation system 4 that discharges exhaust gas after combustion.

The fuel supply system 3 includes a plurality of pulverized coal machines 10 that crush coal to generate pulverized coal, a coal bunker 11 that temporarily stores coal to be supplied to the pulverized coal machine 10, and pulverized coal from the coal bunker 11. A coal feeder 12 as a coal supply device that supplies a predetermined amount of coal to the machine 10, a receiving hopper 13 that receives and stores coal from, for example, a coal carrier, and coal in the receiving hopper 13 to each coal bunker 11. A transport conveyor 14 for transport is provided. In FIG. 1, two pulverized coal machines 10 are provided, and a coal bunker 11 and a coal feeder 12 are provided for each pulverized coal machine 10, but the number of pulverized coal machines 10 and the like installed is this. It is not limited to the embodiment and can be set arbitrarily.

A fuel supply pipe 16 for supplying pulverized coal to a burner 15 provided in the furnace 2 is connected to each pulverized coal machine 10. As shown in FIG. 1, the same number of burners 15 as the pulverized coal machine 10 are provided, and the fuel supply pipe 16 connects the burner 15 and the pulverized coal machine 10 on a one-to-one basis.

In addition, the fuel supply system 3 temporarily stores the woody biomass supply device 20 that cuts the woody biomass and supplies the woody biomass with a particle size equal to or less than the specified value, and the woody biomass supplied from the woody biomass supply device 20. A woody biomass hopper 21 for discharging woody biomass is provided on the transport conveyor 14. The woody biomass discharged from the woody biomass hopper 21 is transported to the coal bunker 11 via the transport conveyor 14. Therefore, coal and woody biomass cut to a predetermined particle size by the woody biomass supply device 20 are mixed in the coal bunker 11, and coal and woody biomass are supplied to the pulverized coal mill 10.

In the present embodiment, the particle size of the woody biomass supplied from the woody biomass supply device 20 is approximately 5 mm or less. The basis for setting the particle size of the woody biomass supplied from the woody biomass supply device 20 will be described later. Further, as the woody biomass supply device 20, for example, a cutter mill that cuts thinned wood or waste wood to a particle size equal to or less than a specified value by a rotating cutter can be used.

Further, in FIG. 1, a transport conveyor 14 is provided in common to the receiving hopper 13 and the woody biomass hopper 21, but what kind of route is used from the receiving hopper 13 and the woody biomass hopper 21 to the coal bunker 11? And whether to transport the woody biomass is not limited to the content of the present embodiment. For example, the woody biomass cut may be discharged directly from the woody biomass supply device 20 to the transport conveyor 14 without providing the woody biomass hopper 21, or the transport conveyor 14 is provided for each of the receiving hopper 13 and the woody biomass hopper 21. The receiving hopper 13 and the woody biomass hopper 21 may be separately transported to the coal bunker 11.

Further, in the present embodiment, as shown in FIG. 1, the woody biomass supply device 20 is provided with a drying function 38. As a result, the water content of the woody biomass is dried to 30 mass% or less, and the particle size is further reduced to a predetermined size or less, so that the retention of the woody biomass in the pulverized coal mill 10 can be suppressed. The drying function 38 includes drying by exhaust heat from the boiler, drying by turbine extraction, drying by new drying equipment, etc., but drying by turbine extraction does not involve major modification of existing equipment or additional fuel input. This is preferable from the viewpoint of economic efficiency.

The ventilation system 4 includes a push-in ventilator 31 that supplies combustion air to the furnace 2 via an air duct 30, a primary air ventilator 33 that supplies primary air to the pulverized coal mill 10 via a primary air pipe 32, and the like. An air preheater 35 that exchanges heat between the exhaust gas discharged from the furnace 2 through the exhaust gas duct 34, combustion air, and primary air, a denitration device 36 that removes nitrogen oxides contained in the exhaust gas, and exhaust gas. It has an electrostatic dust collector 37 that collects the fly ash contained in the air. The exhaust gas from which fly ash has been removed by the electrostatic precipitator 37 is sent to a desulfurization facility (not shown) by an attracting ventilator (not shown) to remove sulfur oxides contained in the exhaust gas, and then a chimney (not shown). Is released into the atmosphere.

The primary air pipe 32 is connected to the bottom of each pulverized coal machine 10. The primary air supplied to the pulverized coal machine 10 is supplied to the burner 15 from the fuel supply pipe 16 connected to the upper part of the pulverized coal machine 10.

The boiler equipment 1 according to the present embodiment is configured as described above. Next, the operation of the boiler equipment 1 will be described. In the present embodiment, a case where woody biomass previously supplied from the woody biomass supply device 20 is mixed in the coal bunker 11 will be described as an example.

In the operation of the boiler equipment 1, first, the push-in ventilator 31 of the ventilation system 4 and the induction ventilator (not shown) are started, and fuel such as light oil for starting the boiler equipment 1 is supplied to the burner 15 from, for example, a fuel pump (not shown). Then, the boiler equipment 1 is raised to a predetermined load. Next, when the boiler equipment 1 reaches a predetermined load and the exhaust gas temperature becomes equal to or higher than a predetermined value, the primary air ventilator 33 is started to warm up the pulverized coal machine 10.

When the warm-up operation of the pulverized coal machine 10 is completed, a predetermined amount of coal is then supplied from the coal bunker 11 to the pulverized coal machine 10 by the coal feeder 12. At this time, the woody biomass previously supplied from the woody biomass supply device 20 is mixed in the coal bunker 11, and the woody biomass is also supplied to the pulverized coal machine 10 together with the coal.

When the level of coal and woody biomass stored in the coal bunker 11 decreases due to the operation of the coal feeder 12 and the pulverized coal mill 10, the woody biomass and coal are discharged from the woody biomass hopper 21 and the receiving hopper to the transport conveyor 14 at any time. It is replenished in the coal bunker 11.

The coal supplied from the coal bunker 11 to the pulverized coal machine 10 is crushed to a predetermined particle size in the pulverized coal machine 10 and connected to the upper part of the pulverized coal machine 10 together with the primary air supplied to the pulverized coal machine 10. It is supplied to the burner 15 from the fuel supply pipe 16 provided. At this time, the woody biomass supplied to the pulverized coal machine 10 is cut to a particle size equal to or less than a specified value by the woody biomass supply device 20, and to a particle size of approximately 5 mm or less in the present embodiment, so that it is the same as pulverized coal. It is crushed by the pulverized coal machine 10 and discharged from the pulverized coal machine 10 along with the primary air, and is burned in the furnace 2 via the burner 15.

When the water content of the woody biomass is 30 mass% or less, the grain size of the woody biomass is set to the specified value or less and supplied to the pulverized coal machine 10, so that the pulverizing capacity of the pulverized coal machine 10 is not reduced and the fireplace 2 is stably supplied. Can supply fuel. However, when the water content of the woody biomass exceeds 30 mass%, even if the grain size of the woody biomass is set to the specified value or less and supplied to the pulverized coal machine 10, the woody biomass may not be crushed and may stay in the pulverized coal machine 10. , It may be difficult to continue the operation of the pulverized coal machine 10. When woody biomass having a water content of more than 30 mass% is used, it is preferable to provide a drying function 38 in the woody biomass supply device 20 as shown in FIG. 1 to dry the water content to 30 mass% or less, preferably 20 mass% or less. More preferred. As a specific configuration of the drying function 38, for example, as shown in FIG. 1, a pipe may be laid inside the woody biomass supply device 20 and a turbine bleed air may be allowed to flow to promote drying by heat transfer. In the case of woody biomass having a water content of more than 30 mass% and less than 45 mass%, the water content of the woody biomass can be reduced to 30 mass% or less even by natural drying, but it takes time, so it is preferable to use the drying function 38. Further, in the case of woody biomass having a water content of 45 mass% or more, it is difficult to reduce the water content of the woody biomass to 30 mass% or less by natural drying. Therefore, it is possible to dry using the drying function 38 as in the present embodiment. preferable. By drying the woody biomass so that the water content is 30 mass% or less in this way, it is possible to suppress the retention of the woody biomass in the pulverized coal mill 10 and to continue the operation. When woody biomass having a water content of 30 mass% or less is used, the woody biomass supply device 20 may not be provided with the drying function 38, or the drying function 38 may not be operated.

In addition, in order to ensure quality, in addition to the moisture measurement of woody biomass before and after drying once every 4 hours, before and after drying when the type and shape of wood are changed. It is preferable to carry out a moisture measurement of woody biomass.

Here, the basis for setting the particle size of the woody biomass supplied from the woody biomass supply device 20, that is, the specified value of the particle size will be described. According to the present inventor, since woody biomass having a particle size of more than about 5 mm is difficult to be crushed by the pulverized coal machine 10, the time from the supply to the pulverized coal machine 10 to the discharge by the fuel supply pipe 16 (residence time). ) Has been confirmed to be much longer than coal. Therefore, when the supply amount of woody biomass having a particle size of more than about 5 mm to the pulverized coal machine 10 is increased, specifically, when woody biomass having a particle size of more than about 3 mass% is supplied, the inside of the pulverized coal machine 10 The amount of woody biomass that stays in the wood gradually increases. As a result, the differential pressure in the pulverized coal machine 10 gradually increases, and finally the operation of the pulverized coal machine 10 cannot be continued. Therefore, as in the present embodiment, by cutting the woody biomass to a particle size of 5 mm or less in advance with the woody biomass supply device 20, the woody biomass can be easily crushed by the pulverized coal mill 10. That is, by supplying the woody biomass to the pulverized coal machine 10 with a particle size of 5 mm or less, it is possible to shorten the residence time in the pulverized coal machine 10 and prevent the differential pressure of the pulverized coal machine 10 from increasing. Therefore, the amount of woody biomass supplied to the pulverized coal machine 10 can be increased to, for example, about 8 to 10 mass% as needed. In such a case, the load of the boiler equipment 1 can be kept constant by reducing the amount of coal corresponding to the total calorific value of the increased woody biomass. The shape of the woody biomass after cutting with the woody biomass supply device 20 is not uniform and tends to be a rectangular shape with a long side (elongated). According to the present inventors, for example, the number of meshes of a standard sieve is 4 meshes. Woody biomass having a particle size sufficient to pass through a sieve (with a sieve opening of 4.76 mm) has a particle size (major axis) of approximately 5 mm or less, and there is no problem even if it is supplied to the pulverized coal mill 10. It has been confirmed. Therefore, the woody biomass supplied to the pulverized coal mill may have a particle size of 4 meshes or more (4.67 mm or less with the mesh size of the sieve) in the standard number of meshes of the sieve. The upper limit of the number of meshes of the standard sieve is not specified, but it is limited because the load of the pre-cutting process increases.

The combustion ash of the pulverized coal and the woody biomass burned by the burner 15 is introduced into the electrostatic precipitator 37 through the exhaust gas duct 34. In the electrostatic precipitator 37, the combustion ash is collected, and the exhaust gas is discharged from the chimney via a downstream attracting ventilator (not shown).

According to the above embodiment, the woody biomass is cut to a particle size equal to or less than the specified value by the woody biomass supply device 20, and the woody biomass is supplied to the pulverized coal machine 10 in order to supply the cut woody biomass to the pulverized coal machine 10. Even if it is supplied, the operation of the pulverized coal machine 10 can be continued. Further, by providing the woody biomass supply device 20 with a drying function 38, when the water content of the woody biomass exceeds 30 mass%, particularly 45 mass% or more, the woody biomass is dried so that the water content is 30 mass% or less, and is specified. Since the grain size is cut to a size equal to or less than the value and the dried and cut woody biomass is supplied to the pulverized coal machine 10, the pulverized coal machine 10 can be continuously operated. Therefore, the co-firing rate of woody biomass, which was conventionally limited to 2 to 3 mass%, can be increased to, for example, about 8 to 10 mass% as needed. As a result, the woody biomass can be efficiently burned in the pulverized coal-fired boiler facility 1 without providing a combustion facility or the like dedicated to the woody biomass.

In addition, by reducing the amount of coal corresponding to the total calorific value of the supplied woody biomass, it is possible to reduce the consumption of coal, which is more expensive than woody biomass, while keeping the load of the boiler equipment 1 constant. it can. Therefore, the running cost of the boiler equipment 1 can be reduced.

In the above embodiment, as the woody biomass supply device 20, for example, a cutter mill that cuts thinned wood or waste wood to a particle size equal to or less than a specified value by a rotating cutter is used, but the woody biomass supply device 20 is used. Can be arbitrarily selected as long as it can be supplied by cutting, crushing, and supplying woody biomass to a particle size equal to or less than the specified value. For example, a shredder or the like that grinds a wood chip having a particle size of about a dozen mm to a particle size (about 5 mm) equal to or less than a specified value may be used.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the ideas described in the claims, which naturally belong to the technical scope of the present invention. It is understood as a thing.

The present invention is useful when burning woody biomass in a pulverized coal-fired boiler facility.

1 Boiler equipment 2 Fire furnace 3 Fuel supply system 4 Ventilation system 10 Pulverized coal machine 11 Coal bunker 12 Coal feeder 13 Accepting hopper 14 Conveyor conveyor 15 Burner 16 Fuel supply pipe 20 Woody biomass supply device 21 Woody biomass hopper 30 Air duct 31 Pushed ventilation Machine 32 Primary air pipe 33 Primary air ventilator 34 Exhaust duct 35 Air preheater 36 Denitration device 37 Electrodust collector 38 Drying function

Claims (1)

It is a pulverized coal-fired boiler facility that burns pulverized coal with a burner.
A coal supply device that supplies coal to a pulverized coal machine,
A woody biomass supply device having a crushing function and a drying function that supplies woody biomass having a particle size equal to or less than a specified value and being dried to a water content of 30% by mass or less to a pulverized coal machine.
A pulverized coal machine that crushes the supplied coal to produce pulverized coal and crushes the supplied woody biomass.
A fuel supply pipe that introduces the pulverized coal produced by the pulverized coal machine and the woody biomass supplied to the pulverized coal machine and crushed into the burner by transporting them in a mixed state using combustion air. ,
Have,
The specified value of the particle size of the woody biomass supplied to the pulverized coal machine is 4 meshes or more in terms of the number of meshes of the sieve.
A pulverized coal-fired boiler facility in which the supply amount of the woody biomass supplied to the pulverized coal machine is 8 to 10% by mass with respect to the total mass of the coal and the woody biomass supplied to the pulverized coal machine. ..

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